A small protest on Wall Street has exploded into a nationwide phenomenon. Will populist demands for jobs, fair taxes and corporate oversight reshape the political landscape?

A protester leads an Occupy Wall Street general-assembly meeting at Zuccotti Park in New York City.

It started in Canada, of all places. The editors of the Vancouver-based anti-consumerist magazine Adbusters called for a Tahrir Square "moment" on Sept. 17 in lower Manhattan to protest what they called the disproportionate power of the U.S. corporate elite. The first responders--a motley collection of punks, anarchists, socialists, hackers, liberals and artists--spent that night in Zuccotti Park, an acre of concrete and greenery near Ground Zero, the New York Stock Exchange and the New York Federal Reserve. Then they did it again. Others noticed: the unemployed and the underemployed, scenesters and community organizers, middle-aged activists and folks who never bothered...